Until recently, the etching of wafers of silicon and the like for the purpose of producing integrated circuit chips has largely been accomplished through the use of plasma. As described in U.S. Pat. No. 4,749,440, etching of such wafers may also be effected through the use of anhydrous hydrogen fluoride and similar halogen gases, diluted with inert gas such as nitrogen, and small amounts of water vapor serving to initiate the etching process. In some instances of etching oxides with hygroscopic characteristics, the existence of inherent moisture in the oxide layer may eliminate the need for adding water vapor.
In the process of obtaining such etching through the use of hydrogen fluoride gas, a suitable degree of control has been obtained in etching away portions of the oxides at the front side of the wafer, in the field and cut pattern being produced on the face of the wafer. However, one side effect of the etching of the wafer has been an uncontrolled amount of etching at the backside of the wafer, particularly in the vicinity of the peripheral edge of the wafer.
In this regard, it has been experienced that maximum etching at the backside of the wafer occurs immediately adjacent the peripheral edge of the wafer, and the degree of etching at the backside of the wafer reduces at progressively increasing distances from their peripheral edge.